1. Field of the Invention
The present invention relates to generally horizontal panel structure for confining blowable insulation material between the joists of a building structure.
2. Prior Art
Various types of insulating materials and methods for applying such materials are known for heat insulating a building structure under construction or constructed. Insulation materials have been supplied as rigid sheets or rolled strips or batts which were secured in position underneath the roof, above the ceiling, inside the walls or under the floor of the structure.
Although older structure-insulating materials and methods continue to be used, there has been increased use of insulation material which may be blown or sprayed into position through a hose, such as particulate or comminuted rock wool, cellulose or fiber glass, or any of various types of particulate or comminuted foams. All of such materials can be referred to as "blowable" or "blown" insulation materials.
A problem with particulate or comminuted blown insulation material is that it settles after installation, decreasing the thickness of the applied insulating layer and reducing the insulating value of the layer. For example, it is known to blow particulate insulation material into the attic of a structure having a horizontal ceiling to be supported by the ceiling. After a period of time the thickness of such layer is reduced by settling of the particulate material to a point where the insulating value of the layer is one-half or less of its original value.
For good reasons, there are at least two situations in which blowable insulation material has not been used extensively. First, blown insulation material has not been used successfully for heat insulating floors because most building structures as built do not have insulation-supporting surfaces beneath the floor. Second, when the roof of a building is close to the building ceiling, such as when inclined roof rafters also function as inclined ceiling joists for an openbeam or "vaulted" ceiling, blown insulation material would substantially fill the space between the roof and ceiling and eliminate air ventilation to the underside of the roof which could lead to premature deterioration of the roof. In addition, cellulose or other particulate paper insulation materials would soak up condensation which reduces its insulation value and may damage the ceiling.